Mulling process



United States Patent M 3,354,486 MULLING PROCESS Arthur Bradshaw,Kenneth Lee, Norman Swales, and Peter Wilfred Voyle, Leicester, England,assignors to United Shoe Machinery Corporation, Flemington, N.J., acorporation of New Jersey No Drawing. Filed Sept. 23, 1964, Ser. No.398,751 Claims priority, application Great Britain, Oct. 26, 1963,42,301/63 4 Claims. (Cl. 12142) This invention relates to a method ofconditioning leather and, more specifically, to a process of mulling ortempering an article of leather to distribute moisture therethrough.

The shoemaking industry has been involved throughout its history in aconstant and penetrating search for technical improvements and, inrecent years, for methods and apparatus which facilitate increasedautomation. One of the principal operations in the shoemaking cyclewhich has impeded the advancement toward complete automation is themulling or tempering of the leather. The purpose of mulling or temperingis to render the leather more workable thereby to permit flexing andstretching thereof. Thus, mulling or tempering is an importantprerequisite to a large number of shoemaking procedures.

Heretofore, a common method employed for mulling or tempering leatherhas been to house the leather in a moist atmosphere for an extendedperiod of time thereby to ensure the distribution of Water throughoutthe leather. Another method of tempering leather was accomplished bydipping it in cold water for a period of hours and allowing it to drain.The result of these operations was uniformly moistened leather which waseasily Worked. The procedure was, however, time consuming and,therefore, costly. Further, it did not lend itself to automation anddiluted the value of the automation of appurtenant operations. The needfor a method of mulling or tempering leather which would facilitate theintegration of these operations into an automated shoemaking cycle hasbeen long felt and desired. Adequate mulling or tempering could not besacrificed for increased automation due to the detrimental efiects onoperations dependent thereon. To do so would be to thwart the purpose ofautomation.

In view of the foregoing, an object of the present invention is toprovide an improved method of conditioning leather which materiallydecreases the time required for the mulling or tempering thereof.

To this end and in accordance with a feature of the present invention,there is provided a method of conditioning leather shoe parts comprisingsubjecting the shoe part to a high temperature moist atmosphere anddirecting a spray of relatively cold water onto the shoe part one ormore times during the exposure of the shoe part to the high-temperaturemoist atmosphere.

The above and other features of the invention will now be described; itbeing clearly understood that the method to be described and claimed isequally applicable to materials used as a substitute for leather.

In order to appreciate the technological advantages and novelty of thepresent invention an understanding of the phenomenon which facilitatesthe implementation of the method is necessary. When a leather article isintroduced to a high-temperature moist atmosphere having a dew pointabove the initial temperature of the article, a film of water isprecipitated on the surface of the article so that condensation forms onthe surfaces of the article. If the article is permeable and if thearticle has not previously been moistened to a level which results inmoisture equilibrium, the film of water will be absorbed and pass intothe interior of the article. The result is a rapid absorption ofmoisture by the article. However, since the article is exposed to thehigh temperature of the atmos- Cir 3,354,486 Patented Nov. 28, 1967phere and the heat of condensation generated by the water film, thetemperature of the article will be gradually elevated until it reachesand passes the dew point of the atmosphere. When the temperature of thearticle passes the dew point of the atmosphere, evaporation of moisturefrom the article will result.

In the application of the method of the subject invention, a leathershoe part is introduced to a relatively hightemperature moistatmosphere. In the preferred embodiment, the atmosphere comprisessaturated water vapor in a temperature range of F. to F. The preferredperiod of exposure is approximately five minutes, i.e. when the otherparameters stated to be preferred are present. This period of exposurefacilitates integration of the mulling or tempering operations into anautomated shoemalring cycle and provides adequate mulling withoutrequiring the use of extreme humidity and/or temperature conditions.

When the leather shoe part initially is introduced to the atmosphere,the dew point of the atmosphere is above the temperature of the shoepart. Accordingly, condensation will initially form on the shoe part andrapidly will be absorbed thereby. This phenomenon will continue at arapid rate until the temperature of the shoe part closely approaches thedew point of the atmosphere.

At a predetermined time during the exposure interval of the shoe part tothe high-temperature humid atmosphere, a spray of relatively cold wateris directed onto the surface areas of the shoe part, i.e. water belowthe dew point of the atmosphere. The exact point during the exposureinterval at which the cold spray is applied is that point at which thetemperature of the shoe part has been elevated to the dew point of theatmosphere. That is, the point at which the formation of condensationwill stop and evaporation will begin. The spray of cold water lowers thetemperature of the shoe part relative to the dew point of the atmospherethereby to effect continued disposition of condensation onto the shoepart. The process may be repeated as many times as is necessary tomaintain continuity in condensation formation. The exact points during agiven exposure interval at which the cold spray must be directed ontothe shoe part is determined by the initial temperature of the shoe partand the dew point of the atmosphere.

In the preferred embodiment of the invention, the water is sprayed ontothe shoe part at relatively low temperature, viz. tap water. Further, itis preferred that the spray of cold water be obtained by atomizing thewater to minimize the disturbance of the high-temperature moistatmosphere. When practicing the method in the preferred embodiment, asingle spray three to four minutes after introduction for from 3 to 15seconds is suflicient to ensure continuous formation of condensation onthe shoe part.

The cold water spray can also be utilized to lower the temperature of ashoe part when it is initially introduced to the high-temperature moistatmosphere or before it is introduced. When the invention is practicedin this embodiment, the shoe part is sprayed with cold water beforeintroduction or just after it is introduced to the atmosphere and may besprayed a second time when the five minute exposure interval has beenapproximately half completed, i.e. assuming the other parameters conformto the requirements of the preferred embodiment.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent of the United States is:

1. A method of conditioning leather comprising subjecting a leatherarticle to a high temperature moist atmosphere and directing relativelycold water onto the article during the period of exposure of the leatherarticle to said atmosphere, thereby to lower the temperature of saidarticle below the dew point of said atmosphere, wherebytoetfectcontinueddisposition of condensation on said article.

2. A method of conditioningleather comprising subjecting a leatherarticle to a high-temperature moist atmosphere having a dew point abovethe initial temperature of the leather article and directing a spray ofrelatively cold water onto the surface areas of the article at leastonce during the period of exposure of the leather article to said*atmosphere, thereby to lower the temperature of said article below thedew point of said atmosphere, whereby to eflfeet continued dispositionof condensationon said article.

3. A method of conditioningleather comprising subjecting aleatherlarticle to a high temperature moist atmos: phere, saidatmosphere being in the temperature range, of 130 F. to- 150 F. andhaving a dew point above the initialtemperature of the leather article,and directing a spray of relatively cold water onto the article duringthe period of exposure thereof to said atmosphere, thereby to lower thetemperature of'said article below the dew point of said atmosphere,whereby to effect continued disposi: tion of condensation on saidarticle.

4. A method of conditioning leather comprising subiecting a leatherarticle to a high temperature moist atmosphere for a period ofapproximately five minutes, said atmosphere being'inthe temperaturerange of F. to F. and having a dewpoint above the initial temperature ofleather article, and directing a spray of relatively cold water onto theleather article at least once during the period of'exposure thereof tosaid atmosphere.

ReferencessCited UNITED STATES PATENTS 2,973,53l 3/1961 Bromfield 12-l423,176,333 4/196'5 Maeser a l2l42 3,203,018 8/1965 Klein 12-142 X PATRICKD. LAWSON, Primary Examiner.

1. A METHOD OF CONDITIONING LEATHER COMPRISING SUBJECTING A LEATHERARTICLE TO A HIGH TEMPERATURE MOIST ATMOSPHERE AND DIRECTING RELATIVELYCOLD WATER ONTO THE ARTICLE DURING THE PERIOD OF EXPOSURE OF THE LEATHERARTICLE TO SAID ATMOSPHERE, THEREBY TO LOWER THE TEMPERATURE OF SAIDARTICLE BELOW THE DEW POINT OF SAID ATMOSPHERE, WHEREBY TO EFFECTCONTINUED DISPOSITION OF CONDENSATION ON SAID ARTICLE.